The present invention relates to a connecting material for anisotropically electroconductive connection for bonding and connecting a semiconductor element having a plurality of electrodes recessed from the outer face of the passivation layer thereof with a substrate circuit board having a plurality of electrodes correspondingly confronting the electrodes of the semiconductor element.
For assembling a semiconductor element, such as a bare chip or the like, on a substrate circuit board, the electrical connection and the mechanical bonding of them may be attained using an anisotropically electroconductive connecting material (in the following, sometimes referred to as ACM). Here, the semiconductor element and the circuit board are held in a posture in which the electrodes or terminals disposed on the semiconductor element and those on the circuit board are in a correspondingly confronted relationship with each other, whereupon the ACM is interposed therebetween. Then, the resulting assemblage is subjected to a heat-pressing to attain mechanical firm bonding of them and an assured electroconductive connection between the correspondingly confronted electrodes simultaneously, while keeping electrical insulation between neighboring electrodes. Semiconductor elements to be connected by such prior bonding practice are provided thereon with protruding electrodes as so-called bumps. The terminals or electrodes on the substrate circuit board are also in a form of protruding patterns. Therefore, the prior technique for bonding and connecting semiconductor elements with a substrate circuit board has been contrived to connect such protruding electrodes with each other.
The recent trend to form electric and electronic assemblies with narrower electrode intervals made with electrodes difficult to be formed as bumps, so that a technique has been proposed to assemble a semiconductor element having electrodes which do not protrude out of the face of the semiconductor element, as dissimilar to the bump, directly on a substrate circuit board. Since such a bumpless semiconductor element is provided with electrodes which recede from the outer face of the passivation layer of the element, it is required to contrive an anisotropically electroconductive connecting material which permits the establishment of an assured connection of the correspondingly confronted electrodes with each other under such a condition.
For meeting such a requirement, an anisotropically electroconductive connecting material comprising electroconductive particles having a hardness lower than that of the passivation layer but higher than that of the electrodes has been proposed in Japanese Patent Kokai Hei 4-30542, in which nickel particles are used as the electroconductive particles. However, the material of the passivation layer harder than nickel is thereby restricted and this prior art connecting material cannot be used for connecting a semiconductor element having a passivation layer made of a resin, such as a polyimide.
The object of the present invention is to provide a connecting material for anisotropically electroconductive connection for bonding and connecting a semiconductor element provided thereon with a passivation layer and having a plurality of electrodes recessed from the outer face of the passivation layer formed on the semiconductor element, on the one hand, with a substrate circuit board having a plurality of electrodes, on the other hand, wherein said connecting material can attain simultaneously a reliable mechanical bonding and an assured electroconductive connection between the correspondingly confronted electrodes without suffering from damage of the passivation layer even in the case where a semiconductor element has a resin passivation layer, while maintaining electrical insulation between the neighboring electrodes.
Thus, the present invention resides in the following connecting material for anisotropically electroconductive connection:
(1) A connecting material for anisotropically electroconductive connection for bonding and connecting a semiconductor element having a plurality of electrodes recessed from the other face of the passivation layer formed on the semiconductor element, on the one hand, with a substrate circuit board having a plurality of electrodes in a correspondingly confronted relation to the electrodes of the semiconductor element, on the other hand, comprising
an adhesive component of insulating property and electroconductive particles,
wherein each of the electroconductive particles comprises a resin core particle coated with a metal layer and the average particle size of the electroconductive particles is at least 1.5 times the recessed depth of the electrode from the outer face of the passivation layer of the semiconductor element.
(2) The connecting material as defined in the above (1), wherein the average particle size of the electroconductive particles is at most 0.5 time the distance between the neighboring electrodes.
(3) The connecting material as defined in the above (1) or (2), wherein the metal coating layer on the resin core particle of each of the electroconductive particles is further coated with an insulating resin.
(4) The connecting material as defined in any one of the above (1) to (3), wherein the hardness (K-value) of the electroconductive particle is in the range from 500 to 10,000 N/mm2.
(5) The connecting material as defined in any one of the above (1) to (4), wherein the Mohs hardness of the metal coating layer of the electroconductive particle is in the range from 1 to 6.